Xerophilic mould fungi on new and historic wood

An examination of mould fungi in 35 medieval and ten 18th Century buildings shows mould growth to varying degrees on different surfaces. The analyses also show a rapid development of mould fungi on certain wooden surfaces in recent years.
A significant difference in the growth between new and old wood is the clearly more extensive growth and different species composition of mould fungi on new wood compared to old wood, despite the short exposure time the new wood had in this study.
Analysis of samples shows large differences in mould growth on new wood compared to historic wood. Mould species found on old wooden materials have ecological growth requirements indicating that the damage is mainly caused by exposure to temporary wet conditions, i.e. Aureobasidium pullulans, Cladosporium spp. and other species with similar requirements. On the new wood there is a dominant occurrence of xerophilic mould fungi, mainly Aspergillus penicillioides. This growth has probably occurred at low values of relative humidity, approx. 70-85% RH.
The proven damage pattern shows two central conditions, a) Wood quality has a major impact on the risk of mould growth, even at the same moisture load, b) Since the historic buildings have had the same use for very long time, recent growth of xerophilic mould species is due to microclimatic conditions that are probably related to climate change.
These findings show the need of thorough knowledge of material properties, microclimate and microorganisms to understand and interpret established mould damage and the risk for future problems due to climate change.